如何为Google服务帐户生成令牌

Question

from google.oauth2 import service_account
credentials = service_account.Credentials.from_service_account_file(
    'service-account.json')
print(credentials.__dict__)

该打印语句打印凭据，但该令牌中的凭据不打印，过期也打印为无。 JSON文件

{  
"type": "service_account"    
"project_id": xxxxxxxxxx     
"private_key_id": xxxxxxxxxx   
"private_key": xxxxxxxxxx   
"client_email": xxxxxxxxxx   
"client_id": xxxxxxxxxx   
"auth_uri": xxxxxxxxxx   
"token_uri": xxxxxxxxxx  
"auth_provider_x509_cert_url": xxxxxxxxxx  
"client_x509_cert_url": xxxxxxxxxx  
}  

请帮助我如何为到期时间的服务帐户生成令牌。